Not trying to sound rude but did you not read the thread Seeky linked? The thread has a portion of info which links a pic that visually shows rotating bits vs shifting bits.
Also included in the thread (at the very beginning) is a link to the Logical Operations thread (which includes the basics of bits/binary) tut which you NEED to know before diving into bit rotation/shifting/etc.
rlwinm deals with bit/binary shifting/rotating plus logical ANDing. Once you understand those two main points, it will make sense.
Hope this all helps as rotation is a bit confusing for beginner PPC coders.
Also included in the thread (at the very beginning) is a link to the Logical Operations thread (which includes the basics of bits/binary) tut which you NEED to know before diving into bit rotation/shifting/etc.
rlwinm deals with bit/binary shifting/rotating plus logical ANDing. Once you understand those two main points, it will make sense.
Hope this all helps as rotation is a bit confusing for beginner PPC coders.